In martial arts the meaning is somewhat different.
The coin is typically given to yudansha (dan rank holders) as a reminder of their achievement and a symbol of their attainment of true advanced student status.
When given to dojo mudansha non-dan rank holders), the coin represented an acknowledgement of that student's potential to excel in the dojo and the art.
Regardless of rank, the challenge coin serves as a easily hidden reminder to the practitioner they ARE a martial arts practitioner and are expected to conform to the highest of morale and ethical standards. This is best embodied in the slogan "Karate ni sente nashi" or "There is no first attack in karate."
This does not actually mean for you to allow the other person to strike first but, as Nagamine Hanshi explained it. "Don't be there."
Don't be where trouble might start. If you're not there then there is no danger of you having to strike first.
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